This invention relates to medical syringes with hypodermic needles and, more particularly, to apparatus for sealing a lumen bore of a syringe lumen communicating between an interior of a syringe body and a hypodermic needle carried by the lumen to prevent a second use of the syringe comprising, a lumen spike moveable by a plunger/piston of the syringe between a retracted position allowing fluid to flow from the interior of the syringe body to the hypodermic needle and a sealing position disposed within the lumen bore preventing fluid from flowing from the interior of the syringe body to the hypodermic needle. In a single use syringe having a lumen bore of a syringe lumen communicating over a connecting path between an interior of a syringe body and a hypodermic needle carried by the lumen and a valve member blocking the connecting path after a first use of the syringe to prevent a second use of the syringe it also relates to a fail-safe improvement for preventing the connecting path from being subsequently unblocked to allow more than one use of the syringe comprising, a portion of the syringe body carrying the lumen and the valve member when the valve member is blocking the connecting path being frangible when subjected to a force f.sub.1 thereby separating the lumen from the syringe body; and, the valve member being resistive against unblocking the connecting path to a force f.sub.2 which is greater than f.sub.1 whereby the portion of the syringe body will fracture and separate the lumen from the syringe body before the valve member unblocks the connecting path. It further relates to a unitary plunger/piston for use in a cylindrical syringe body of internal diameter d.sub.1 comprising, a plastic plunger shaft portion having an integral cylindrical piston portion of a diameter d.sub.2 equal to or smaller than d.sub.1 formed at an inner end thereof; and, annular sealing means of a diameter d.sub.3 greater than d.sub.1 carried by the piston portion for compressing against internal sidewalls of the syringe body.
Needle-borne pathogens such as staph, hepatitis-B, and HIV have made single use syringes a virtual necessity. Even in areas where needles are provided free to illegal drug users, there is a problem with multiple uses of needles. Users high on drugs or in need of an injection simply will not take the time to get a new needle. And, unfortunately, sometimes the free needles are not available or available in necessary quantities. Whatever the reasons, it is a problem that must be faced.
Some public health areas are also facing problems of multiple needle use, even among medical workers. Whether by accident or intent, the use of a syringe on more than one patient is simply not something that can be tolerated in the presence of the many needle-transmitted pathogens that can be present in today's environment.
Single use syringes, per se, are not new technology. There are several factors that must be considered, however, and present technology does not satisfy all the necessary criteria. Price is probably the single most important factor. While not too many years ago all injections were done with reusable metal and glass syringes and replaceable needles that were intended to be autoclaved between uses, virtually all injections are now performed with single use plastic syringes that sell for only a few cents each and are intended to be disposed of after use. Thus, to be financially viable, single use syringes must not add very much to the selling price. If not mandated by law, a single use syringe that is over a threshold price acceptable to the financial interests determining what is bought and what is not, will not be purchased. If mandated by law, the financial interests will mandate that the lowest price syringe meeting the letter of the law be purchased--whether it works well for its intended purpose or not. While not an ideal situation, those are simply the facts of life which must be faced by anyone trying to solve the ultimate problem.
Particularly because of the illegal drug users, a viable single use syringe must be absolutely one-use in design and not merely inconvenient to reuse. If it can be made to work again, the illegal drug user will do so. After price, this should be the most important factor to anyone actually trying to solve the ultimate problem. This means that if a single use syringe can be made to work again, the drug user will make it work. Single use syringes must also be considered from two perspectives. There is a need for syringes that can be provided directly to illegal drug users which can only be used once. There is also a need for syringes that are used by others and then disposed of, which may fall into the hands of illegal drug users either intentionally or unintentionally. And, the problems are not the same. It can be assumed that medical workers, diabetics, and the like, will follow the designated protocol for use of a syringe. Thus, they should activate any single use provisions incorporated into the syringe. Such syringes should not be given directly to illegal drug users as they will most likely be instructed by someone who has figured it out, how to use the syringe without activating the single use provisions. Ideally, syringes given directly to illegal drug users should activate upon use in any manner, even if the injection is partially or totally incomplete as a result of misuse.
Finally, those syringes intended for medical use and not first use by illegal drug users must be normally usable; that is, it must be able to function in its normal manner when employed for its single use. A 3 cc syringe that can only be used for up to 1 cc and acceptable to an illegal drug user is simply not acceptable for the general medical marketplace.
In this regard, while it is the illegal drug users and a few others that are causing the problem and requiring a solution, in order to be effective against the few, the whole community of injection users is going to have to adapt to new technology. If a source of multiple-use needles remains, the drug-users will get them--either directly by stealing or by creating an expanded illegal industry in needle trafficking. For example, one recent unconfirmed report stated that a "clean" needle can bring up to twenty dollars in New York City. Thus, users like diabetics will be forced to pay more for their needles and will have to use single-use needles to prevent the subsequent sale of their used needles to illegal drug.
As will be seen from the discussion of the prior art that follows, it is virtually impossible to come up with a single use syringe that is both economically feasible and absolutely fail-safe in the hands of an illegal drug user as the first user. Thus, it makes more sense to address the larger problem of a single use syringe that is both economically feasible and absolutely fail-safe in the hands of an illegal drug user (or anyone at all for that matter) as a second-in-time potential user.
Several known prior art syringes related to this problem and its solution will now be discussed and their shortcomings identified.
U.S. Pat. No. 4,838,870 of Haber et al. is directed to a syringe in which the hypodermic needle is grabbed by the plunger at the bottom of its stroke so that as the plunger is withdrawn, the needle is pulled into the syringe body. The intent is to make it safe to dispose of the syringe since the needle is now housed within the syringe body. If one were to try to use the Haber et al. syringe as a single use syringe, the plunger could be removed and the needle reinserted if a used syringe. In either case (new or fixed), the gripping fingers could be snipped off to bypass the needle being withdrawn during further use.
A similar structure and situation exists with U.S. Pat. No. 5,125,899 to Frignoli. In this case, however, Frignoli intends that his syringe be a single use syringe. As with the Haber et al. syringe, however, a new Frignoli syringe could have its single use capability disabled relatively simply. A used Frignoli syringe might be slightly more difficult to reassemble; but, could probably be made at least usable for an illegal drug user's use with a pocket knife and perhaps a bit of glue. In this regard, it must be remembered that the regaining of functionality (and not beauty or sanitation) is the end goal of the drug user.
PCT/FR90/00826 is a simple and inexpensive approach to solving the problem. The syringe nozzle has an external barbed front portion frangibly attached to the back portion. The needle hub has internal barbs that permanently attach it to the front portion. In use, an extension on the piston pushes the front portion and breaks the frangible attachment. If new when in the hands of the illegal drug user, snipping off the extension disables the single use aspects of the syringe. If used, the extension can be snipped off and then the needle hub reattached with silicone rubber adhesive, epoxy glue, or the like--easily stolen from a hardware or drug store.
PCT/AU91/00394 discloses a valve for a syringe intended to render it a single use device. A number of embodiments are disclosed. A first reaction is that regardless of how effective any or all of the embodiments are, the cost of manufacture and sale will be too high to be salable in the marketplace if there is a less costly substitute. It would also appear that the valve could be disabled by driving a nail, ice pick, or the like, through it from the lumen. It must be remembered that all that is required to reestablish functionality is to make the valve leak.
Bartlett et al. (U.S. Pat. No. 5,254,093) is like PCT/AU91/00394 above. The cost of manufacture and sale would be prohibitive as against any simple and cheap device that works at all. It also appears that a resourceful individual with a pocket knife and a little glue could amputate the valving arrangement and reattach the needle to the end of the syringe body. Such an approach might be ugly, but it should be functional.
U.S. Pat. No. 5,000,735 of Whelan employs both a ball valve and a disconnecting piston to render the subject syringe single use. As with other valves, all that is required is to make the valve seat leak. A nail or ice pick could to that quite nicely even if the ball remained trapped. And, the plunger could be reattached with a bit of silicone rubber adhesive. As another observation, the valve 94 could not be molded by inexpensive molding techniques. Thus, if manufacturable at all, the cost of manufacture would be prohibitive to successful sales.
The apparatus of Jaffe et al. disclosed in U.S. Pat. No. 5,067,942 is another example of high cost of manufacture. The hypodermic needle has a closed inner end with side ports that are covered by a retractable sleeve. Once the syringe has been used, the retracting mechanism for the sleeve is disabled so that the ports remain covered. Hypodermic needles are manufactured in large volumes by automated machinery designed to take lengths of tubing, cut them to length, and sharpen one end to a bevel. They are not designed to seal the opposite end and put a port through the sidewalls. That factor alone would make the Jaffe et al. syringe design financially undesirable to any major manufacturer of syringes.
The approach of Yerman in U.S. Pat. No. 4,233,975 is the closest prior art to the approach of the present invention as will be seen. Yerman has a male member carried by the opening to the lumen. When the plunger is depressed, it forces the male member into the opening to the hypodermic needle thereby blocking it from further use. There are several embodiments including one in which the end of the piston acts as the sealing member and the piston becomes detached from the plunger. As with many of the above-described approaches, Yerman disposes a valve mechanism over the opening to the needle. Thus, like the other needles with valves, all that is required is to make the valve leak to work. The Yerman syringe could also be disabled as to its single use function by inserting a long screw into the body after removing the piston, threading it into place, and pulling out the parts interfering with normal operation. The various embodiments as depicted would also be difficult to impossible to injection mold inexpensively and, therefore, the Yerman syringe would not likely be financially viable.
Wherefore, it is the object of this invention to provide a low-cost and effective single use syringe.
It is another object of this invention to provide a single use syringe that cannot be reworked to make it reusable.
It is yet another object of this invention to provide a single use syringe that incorporates highly effective fail-safe provisions.
It is still another object of this invention to provide a single use syringe which functions by permanently blocking the fluid path to the hypodermic needle.
It is a still further object of this invention to provide a single use syringe that is first used by medical personnel or the like following accepted use protocols so as to completely and uniformly active the single use and fail-safe provisions of the syringe thereby preventing a second use of the syringe under virtually any circumstances.
Other objects and benefits of this invention will become apparent from the description which follows hereinafter when read in conjunction with the drawing figures which accompany it.